Mechanical position finder



Jan. 10, 1950 GQsWIF'r MECHANICAL POSITION FINDER 2 Sheets-Sheet 1 Filed March 26, 1945 FF w lflfarn INVENTOR. GILBERT SWIFT W Jan. 10,- 1950 G. SWIFT 2,493,786

MECHANICAL POSITION FINDER Filed March 26, 1945 2 Sheets-Sheet 2 INVENTOR. GILBERT SWIFT.

' r(fi I- 77 Patented Jan. 10, 1950 UNITED STATES PATENT OFFICE 2,493,786 -MEOHA NIQ4 1L rosrrron FINDER Gilbert Swift, Red Bank, N, J.

Application :March '26, .1845, .Serial :No. 1585;(11 6 c aim (01. 334F189) (Granted under the act of March 8, 11883, as amended April 39, 1928; 3.70 1G. #57) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

This invention relates to improvements in :geoe metrical instruments.

There are varioussystems for locating the posi: tions of ships, aircraft, land vehicles, etc. For simplicity I-shall discuss my present inventionin this specification with reference to a system for locating land vehicles, but it is to be understood that it is not thereby intended 'to limit my invention to such system or such use.

Said system utilizes three radio transmitting stations, located at known geographical positions. Qne of :these I shall denote as the master stationpor M, and the other two as slavefstae tions, or S1 and S2. M sends out a radio signal and S1 and S2 pick up this signal and retransmit itso that the same signal is being sent out by the three stations. A land vehicle, which I shall call 'V, whose geographical .posi-. tion is to be determined, is equipped withsuitable radio receiving and timing apparatus. 1 This apparatus receives the signals from the three stag tions M, S1 and S2 and indicates the time difienence between its receipt directly from M and its receipt from each of S1 and. S2.

The signal will travel directly from M to V. It will also travel from M to S1, and at S1 it will be received and retransmitted, and will then. travel from S1 to V. Its velocity will be 186,300 miles per second or, in round figures, one mile in five microseconds (which figure I will use in the followin specification). The time of transmission of the signal from M to V Will be solely dependent upon the distance The time of transmission of the signal from M through S to V will be the sum of three components: (a) The time for the signal to travel from to 8;,

dependent upon the distance MS1; (b) the time for .the signal 130 be received and retransmitted at S1,-dep.endent upon the time lag in-the circuits of the receiving and retransmitting apparatus located at S1; and (c) the time for the signal to.

mait will be the difference between :the

tances andSrV. If said remainder is positive, it will indicate that V is closer to M than to S1; if negative, that V is closer to S1 than to M. Thus, a hyperbola may be constructed geometrically, -or may be selected from a family of hyperbolas prepared beforehand, all points of which will be further from S1 than from M, or vice versa, by said distance. V will be located at some point along said hyper-bola.

If the same procedure is repeated with respect to the other slave station S2, another hyperbola will be obtained at some point of which V is also located. V will, therefore, be located at the intersection of the twohyperbolas. If there are two points of intersection, it will ordinarily be easy to decide which one indicates the true position, as the other point will usually be so far from the area where the vehicle V could be as to eliminate it, :or other circumstances or means will determine the correct point.

It is an object of the present invention to provide a mechanical plotting instrument which will simply, rapidly and accurately locate the point where the two hyperbolas', aforesaid would intersect,:;but .withoutt-he necessity of actually constructing or determining the hyperbolas themselves. I

It is also an object of the present invention to provide a geometrical instrument which will ascertain the intersection or intersections of two hyperbolas wherein the :points of generation and the constant difference in the distances from said points to each :hyperbola are known.

Other objects and uses will appear from the following specification.

In :the drawings:

Figure 1 :is a perspective view of a plotting in.- strumfint, embodying my invention, in operative position upon ;a map;

Figure 2 is a plan view :of the map of Figure *1, he dis nces being indicated;

,Figures 3, l4 and '5 are enlarged plan, front ele, vational, ,andmightend elevational views, respec tively, of one of the slides of Figure 1, in operative position on one :of the arms;

Figure 6 is an-enlarged fragmentary plan view of theswivellshackle of :Figure 1, the knob having been removed;

vililigure i7 is anelevation'alongline 1.--.-1 of ure 6,;

' Figure :8 is a perspective view, partly broken away, of one Movie .and onespring of the swivel hackle oi Figures .6 andz'l; and

Figurefi is an-elevation oft-he pinion gear unit of ithesswivehshackleaof rligures 6 and shackle I9. 'The plotting instrument II is used,

on a plotting board 2| to which is fastened a map 23 and three station markers 25.

The three arms I3 are identical, each being an.

elongated rectangular metal bar having scale markings 21 on its upper surface and gear teeth 29 all along one side to form a rack. In the pre ferred embodiment of my device, the scale markings 21 run from 65 to 130, the units being equal to miles on the scale of -the maps" with whichit is used; However, the numbering is V arbitrary and may be'changed to suit other requirements. Extending downwardly from one end of each arm I3is a rod-like supporting finger I5, the three fingers I5 being similar, but of different lengths, so as to maintain the arms I3 at different heights above the map 23, as will befurther discussed below. The lower ends of the fingers I5 rest upon the map 23, and are rounded so as not to tearit.

Thethree slides I I (Figures 3, 4 and 5), are identical, each consisting of a rectangular metal base 3I'having two longitudinal flanges 33, extending upwardly and then inwardly toward each, other so' as to form a longitudinal channel 35 therebetween. The channel 35 slidably accom-' modates one of the arms I3. Etched; across the flanges 33'; midway between their ends, is a hairline 31, used in positioning the slide I! relative to the scale markings 21 on one of the arms I3; Secured to the mid-point of one side of the base 3| of the slide lTis a depending cylindrical pivot 39." Attached to the base 3| bya through rivet 4 I ,is a spring steel strap 43, which extends along one side of the base, being curved outwardly at its central portion 45'so as to pass around the Pivot 39." The strap 43 is disposed at an angle so that a' horizontal detent 41, attached to it at one end, extends througha hole in'one' of the flanges 33 and impinges against the gear teeth 29 of one of the arms l3. Said'detent 4T locks the slide H at any desired point along said arm IS. The slide may be's'lidably repositioned on its arm |3 by retracting the detent 41 by means of a detent handle49.1

The swivel shackle I 9 (Figures 6 and f7) ismade up of three identical, independently rotatable cleViSes 5| (Figure 8) and a pinion gear unit 52 (Figure ,9). Each clevis 5| comprises a rectangular back wall 53, having a vertical, fiat inner surface 55 and two relatively'thin, horizontally disposed, triangular flanges 51;exteriding outwardly .from said wall 53 normal to said surface 55,*the

flanges being pierced by circular apertures 59, which are in'register. Passing through the apertures 5'9 of all three clevises 5 Us a pinion shaft 6| (Figure '9'). Integral, axially, with said shaft 6| are three identical pinions 63, and two identical annular separators 65, alternatelydisposed and the map 23 upon which it rests. In mypreferred embodiment, the pinion gear unit 52, comprising the pinionshaft BI, the three pinions 63, thetwo separators 65 and the pointer 69 are made up from a single piece of metal. Also the apertures 59 are large enough to pass the pinions 63, so that the parts may be assembled for operation.

Each pinion 63 fits between the flanges 51 of one of the three clevises 5 I, the pinions 63 and clevises 5| being disposed at successive heights above the map 23 corresponding to the positions of the arms I3 as already mentioned. The separators 65 fit between adjacent clevises 5| so as to allow individual rotation of each clevis. Along the surface '55 of each clevis 5| is an arcuate leaf spring 1| (Figure 8) which is bent over the wall 53 at each end. Extending horizontally, between the flanges 51 of each clevis 5|, is one of the arms I3, its gear teeth 29 being kept in mesh with one of the pinions63 by the spring 1!. The three arms I3 are identically positioned longitudinally in their respective clevises 5 I, so that, in any operative position, the same scale number on each of the three arms I3 is abreast of the pinion shaft 6|; When the knob 61 is manually rotated, all three pinions 63 rotate with it, thereby causing the three arms I3 to move uniformly, longitudinally through the.

swivel shackle I9. As'the three clevises 5| are individually rotatable, the three arms I3are likewise individually rotatable about the pinion shaft 6|.

The plotting board 2| is a flat rectangle of wood, large enough to accommodate the maps to be used. The map 23, laid out in rectangular coordinates, covers the locality of the three radio transmitting stations M, S1, S2 and is of a scale scale markings 21 on the arms I3.

Secured by screws to the map 23 and plotting board 2|, directly over the geographical positions of the three stations M, S1, S2 are three station markers 25. Each of said markers 25 comprises a' skeletal disc 15, cut away so as to leave as much of the map 23' exposed to view as possible, and four upwardly-extending legs 11, terminating in a cylindrical boss 19; Said boss I9 has an axial vertical bearing 8 I, adapted to rotatably support the pivot of one of the slides". The three markers 25 are'alike, except that they are of different heights so as to cooperate with the three fingers I5, similarly graduated in height, as already noted, to maintain the three arms I3 at successive levels (Figures 1 and 7) above the map 23, so that the'racks on said arms may be in mesh with the three pinions 63 and so that said arms may be operatively rotated in planes parallel to the map without mutual interference.

In the operation of my device, if the slides 25 are positioned upon their respective arms l3 so that the scale readings on the arms extending to M and S1 differ by the difference between the dis tances MV and 81V, andthe scale readings on the arms extending to M and S2 differ by the difference between the distances MV and 52V, and if the three pivots 39, on the three slides I1, are in place in their respective bearings 8| of the three station markers 25, then the pointer 69 will indicate the position of the vehicle V on the map 23.

The steps to be taken to determine this position are best illustrated by a specific example.

Figure I2 (a plan view of the map 23 of Figure 1') indicates the distances as used in the specific; The arms I3 of the plotting instru' example. ment I| used in the example are numbered from 65 to 130, as previously described. I The time enemas lent to .6 TIherehasbeen written (as is my usual praoti'ce'in using my invention) on the map the constants which have beenidetermined'in ad'- Wamce. Thusat-S1 thereappears the figure"-10:6, which is the sum of the distance MS1 (-l0. and the distance (.6) equivalent to the time lag at S1. Similarlyrthe-figure 30.6 CL-4-56) appearsat S2.

The operator at :vehicle -V, located at the place indicated in Figure 2, ascertains from the receiving and timing apparatus' that-a signal is received 28 microseconds later from -S1 than from M, and 203 microseconds later from S2 than fromM. The timing apparatus is so calibrated that it computes the time difference in their distance equivalents (5.6 and 40.6 respectively) and also increases them by 100 (as I have arbitrarily chosen "100 as the base number) so that the actual readings will be 105.6 and 140.6 respectively. The slide H on the center arm l3 will be set at the base number 100 of the scale markings 21 on that arm and its pivot 39 will be positioned in the bearing 8| of the station marker 25 at the station M. In order to ascertain the setting for the slide Won the left arm [3, which will extend to S1, the operator will subtract the constant for S1 (as determined beforehand and written on the map) from the difference of time of reception of a signal from M and from S1 (as indicated by the timing apparatus), or 105.610.6=95. The slide I! on the left arm I3 is accordingly set at 95 on that arm and the pivot 39 of said slide is dropped into place in the bearing 8| at S1.

A similar computation for S2 will be l40.630.6=1l0. The slide I! on the right arm l3 will accordingly be set at 110. It will now be necessary to adjust the instrument ll so that the pivot 39 on the right arm l3 will drop into place in the bearing 8| at S2. To accomplish this, the knob 61 is manipulated until the pivot 39 drops into place. The pointer 69 will now indicate the location of the vehicle V.

Upon measurement on the map, the vehicle V will be found to be 25 miles from M, 20 miles from S1, and miles from S2. It will be noted that the five unit difference between the settings (100, 95) of the slides I! on the arms I3, extending to M and S1 respectively, indicates the actual five miles difference in distance between MV and 81V; and the ten unit difference between the slide settings (100, 110) on the arms l3, going to M and S2 respectively, indicates the actual ten mile difference in distance between MV and SzV. The setting on arm I3, extending to S1, is in a negative direction (less than 100) as V is nearer to S1 than to M; the setting on arm l3, extending to S2, is in a positive direction (more than 100) as V is further from S2 than from M.

It is thus seen that the operator at V need but perform two simple subtractions to locate his position with my instrument. Such simplicity is particularly advantageous in determining the position of a military vehicle in time of battle. The operator at V need know nothing about the technical operation of the system or the geometrical construction of hyperbolas. The actual operation of my instrument on a plotting board need not even be done at the vehicle, but may be done at a base station to which the time difierences indicated by the timing apparatus may be relayed by radio.

Although I have described a system utilizing three stations and an embodiment of my invention having three arms and associated parts, it

nected. for'zmntual op'erational rotation; tthree. markers respectively positioned. along said tracks,

the positions of 'atzleast two of said markers being adjustable. r I

instrument are determine an intersection of two hyperbolas, comprisingapinionmember; three tracks, in mesh with said pinion member and individually rotatable about said pinion member; a pivot on one of 'said racks; two pivots, respectively longitudinally positionable along the other two of said racks; two means to'rrotatabtysustain two of said pivots; a pointer, sustained by the pinion member.

3. A position determining instrument, comprising three elongated arms; a shackle member in engagement with said arms, said arms being conjointly, uniformly, and longitudinally movable with respect to said shackle member, and at least two of said arms being individually rotatable about an axis of rotation extending through said shackle member, said axis of rotation being normal to the longitudinal axes of said arms; three markers; three pivots, one attached to each of said arms, at least two of said pivots being movable to a plurality of positions along at least two of said arms, and said three pivots respectively being engageable with said three markers.

4. Aposition determining instrument, comprising three elongated arms, a shackle member in engagement with said arms, said arms being conjointly, uniformly and longitudinally movable with respect to said shackle member, and said arms being relatively rotatable in parallel planes, about an axis of rotation normal to said planes and running through said shackle member; three markers; a pivot attached to each of said arms, at least two of said pivots being movable to a plurality of positions respectively along at least two of said arms, and said three pivots respectively being engageable with said three markers.

5. A position determining instrument, comprising a map; three markers on said map; three elongated rack members rotatably disposed in successive planes above said map; three pivots engageable respectively with said three markers, each of said pivots being slidably attached to one of said rack members, whereby said pivots may be positioned respectively at a plurality of points along said rack members; means to lock each of said pivots at any of said points; and shackle means, said shackle means including three individually rotatable clevises to respectively retain the three rack members, pinion means in engagement with said rack members, and means to actuate said pinion means whereby to move said rack members uniformly longitudinally relative to said pinion member.

6. A geometrical instrument, comprising a pinion shaft; means to rotate said'shaft; three pinions, uniformly rotatable upon rotation of said shaft; three clevises mounted upon said shaft and individually rotatable about said shaft; a pointer mounted upon said shaft; three elongated arms; each arm being provided with a rack, and scale markings, and a depending finger; each arm extending through one of said clevises; each rack being in mesh with one of said pinions; each arm being individually rotatable about the 7 pinion in mesh with its rack; each arm being longitudinally movable through one of said clevises upon rotation of said shaft; three slides mounted respectively upon said arms, said' slides being respectively slidable longitudinally to a plu- '5 rality of positions along said arms; means to retain said slides at any of said positions; indicating means upon each of said slides for indicating its position relative to the scale markings REFERENCES CITED The following references are of record in the file of this patent:

Number 1,046,362 1,661,095 2,026,459

10 Number 8 UNITED STATES PATENTS Name Date Adams Dec. 3, 1912 Rowe Feb. 28, 1928 Caretta Dec. 31, .1935 Linkowski Aug. 8, 1944 FOREIGN PATENTS Country Date France Nov. 2'7, 1911 Great Britain Feb. 12,1931 France July 9, 1934 

